The present application claims priority to Japanese Application No. P11-082375 filed Mar. 25, 1999 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
This invention relates to a non-aqueous electrolyte battery and, more particularly, to a non-aqueous electrolyte battery having improved low-temperature characteristics and preservation performance.
2. Description of Prior Art
Recently, a wide variety of portable electronic equipment, such as a camera built-in video tape recorder, portable telephone or a lap-top computer, have made their debut, and attempts are being made to reduce their ize and weight. As portable power sources ofthese electronic equipments, researches and development for improving the energy density of the batteries, in particular the secondary batteries, are going on briskly.
The batteries employing the non-aqueous electrolyte, in particular the lithium ion secondary batteries, are able to develop a higher energy density than is possible with a conventional secondary battery employing an aqueous electrolytic solution, such as a lead battery or a nickel cadmium battery. For this reason, the prospect for the lithium ion secondary batteries is favorable and the market therefor is increasing rapidly. With the expansion of the market, the operating conditions for the batteries are becoming diversified. In particular, the demand for using the batteries under low temperature is increasing rapidly. Also, as the operating conditions for the portable electronic equipment are diversified, there is raised an increasing demand for the preservation capability of the batteries.
However, up to now, the low-temperature characteristics for the non-aqueous electrolyte secondary batteries are not sufficient, whilst the preservation characteristics thereof leave much to be desired. For this reason, there is raised a strong demand for a technique for possibly improving these characteristics.
It is therefore an object of the present invention to provide a non-aqueous electrolyte secondary battery having improved low temperature and preservation characteristics.
In one aspect, the present invention provides a non-aqueous electrolyte battery including a negative electrode containing a carbon material as a negative electrode active material, a positive electrode arranged facing the negative electrode and which has the negative electrode containing a positive electrode active material, and a non-aqueous electrolyte interposed between the negative and positive electrodes. The negative electrode contains a material not doped with or releasing lithium in an amount not less than 20 wt % and not larger than 40 wt % based on the negative electrode active material.
According to the present invention, in which a compound not doped with nor emitting lithium is contained in the negative electrode active material, there is provided a non-aqueous electrolyte battery in which the temperature of the negative electrode active material is not lowered thanks to the temperature keeping effect of the compound, even if the environment of the battery is at a lower temperature, thus keeping an optimum battery performance.